Gilda H. Loew

QUANTUM CHEMICAL CALCULATIONS ON THE TWO‐STEP MECHANISM OF PROFLAVIN BINDING TO DNA*

Quantum chemical calculations on the binding of proflavin to DNA lead to a model in which the outside binding to a phosphate group leads to an induced fit in the intercalation receptor site. The calculations suggest hydrogen bonding of the amine groups of the outside bound proflavin to the anionic oxygen of the backbone phosphate. The resulting partial neutralization facilitates the conformational transitions required for intercalation. The results are consistent with the observed preference of proflavin for dCpdG over dGpdC sequences and with the observed kinetics of the binding reaction.

Evidence for α-keto-enol tautomerism in reduced acetylisoalloxazines

Abstract The spectra of fully reduced 6- and 8-acetyl-10-methylisoalloxazine display anomalously intense absorptions near 500 nm that are not characteristic of the expected 1,5-dihydro reduction products. The reduced absorbing species are characterized as α-enol tautomers on the basis of correspondence with predictions from INDO/S spectral calculations. The spectral calculations used geometries optimized within the framework of the semiempirical MNDO method.